Breath alcohol detection devices typically include a computer system for determining breath test results and storing information concerning breath tests for subsequent retrieval, a handheld measurement module connected to the computer system for conducting the test and an ignition interlock which deactivates the vehicle ignition unless a breath test determines that the breath alcohol content (BrAC) of the prospective operator is less than a specified limit. A breath test is performed by connecting a breath tube to the module and having the prospective operator blow breath through the tube and into the module for a sufficient length of time to assure alveolar air has been flowed to the module. A breath test is then conducted on alveolar air to determine the BrAC of the prospective operator.
Many conventional alcohol breath test devices use vacuum pumps to draw breath to be sampled into a detector to determine the BrAC of the prospective operator. These devices include multi-part alcohol modules including the pump and are complicated and expensive.
U.S. Pat. No. 6,167,746 discloses a breath alcohol detection device in which breath is flowed through an induction tube. A sample of the breath in the tube is flowed into a fuel cell to determine the BrAC of the person being tested. Flow to the fuel cell is controlled by opening and closing a valve. A computer system determines the interval the valve is opened based on the pressure in the induction tube after the valve is opened so that a required volume of breath is flowed into the cell.
Accordingly, there is a need for an alcohol breath test device having an improved alcohol measurement module. The module should be made from a single body of rigid material, preferably plastic. Passages required for flowing breath and sample portions of breath should be formed by molding or milling of the body to eliminate manufacturing and assembly cost. The body should support the fuel cell and sensors required to conduct the breath test yet should be sufficiently small to form part of a handheld module easily held by a prospective operator in order to conduct a breath test. The module with the improved block should be resistant to tampering by the prospective operator. There is also a need for an alcohol detection device where the test is performed without creating a pressure pulse which signals to the prospective operator that the test is being taken. There is also a need for a compact alcohol detection device with components mounted in a compact body.